When a mobile station in a mobile communication system enters a communication network, the mobile station searches a base station in the network, and then attempts to get an initial network access. However, the base station does not recognize at the initial stage of the network access, and does not transmit a signal to the mobile station via a designated channel for the mobile station to inform network configuration information. Therefore, the base station should transmit the network configuration information through a superframe header (SFH), which can be also called as a broadcast channel (BCH) in this document. However, if the mobile station does not know the location and size of the SFH, the mobile station cannot decode the SFH and fails to get an access to the network. Therefore, it is necessary to pre-define the size and location of the SFH so that the mobile station can decode the SFH.
In a cellular orthogonal frequency division multiplex (OFDM) wireless packet communication system, uplink/downlink packet transmission for data and/of control information is made on a sub-frame basis and one sub-frame is defined by a certain time interval including a plurality of OFDM symbols.
A basic frequency time resource building block is called as ‘resource unit (RU)’ in IEEE 802.16 standards or as ‘resource block (RB)’ in 3GPP LTE (3rd Generation Partnership Project Long Term Evolution), both of which adopt an orthogonal frequency division multiple access (OFDMA) scheme. A RU comprised of a predetermined number of sub-carriers and OFDMA symbols.
The RUs in physical frequency domain is called as physical resource units (PRUs). The PRUs are mapped to so-called logial resource units (LRUs), which are in one-to-one mapping relationship for the sake of efficient resource management. A mapping relationship between the LRUs and the PRUs can be described on a sub-frame basis. Also, the mapping relationship between the LRUs and the PRUs can be described using a pre-defined mapping relationship between indexes of the LRUs and indexes of PRUs.
The LRUs are further classified into contiguous resource units (CRUs) and distributed resource units (DRUs). If a scheduled number of CRUs are allocated for a mobile station, the CRUs are mapped to a group of PRUs which are contiguous in physical frequency domain. On the other hand, if a scheduled number of DRUs are allocated for a mobile station, the DRUs are mapped to a plurality of PRUs which are spread over the physical frequency domain.
To spread the DRUs over the physical frequency domain, a predetermined permutation rule designed for obtaining frequency diversity gain can be used. Permutation may be considered to be a mapping process of a set of elements to other elements of the same set, i.e., exchanging (or “permuting”) elements of a set. Alternatively, permutation can be regarded as an assignment operation, with the indexes of a set of the PRUs assigned to the indexes of a set of the DRUs. Or, the permutation can be regarded as an index reordering process for a set of elements with indexed.
The DRUs are generally used for the scheme called as frequency diversity scheduling (FDS) scheme and the CRUs are generally used for the scheme called as a frequency selective scheduling (FSS) scheme. The FDS scheme is a transmission scheme that obtains a reception performance gain through frequency diversity, and the FSS scheme is a transmission scheme that obtains a reception performance gain through frequency selective scheduling.
In the FDS scheme, a transmission stage transmits one data packet over sub-carriers widely distributed in a system frequency domain so that symbols in the data packet can experience various radio channel fading. Therefore, an improvement in reception performance is obtained by preventing the entire data packet from being subject to unfavorable fading. In contrast, in the FSS scheme, an improvement in reception performance is obtained by transmitting the data packet over one or more consecutive frequency areas in the system frequency domain which are in a favorable fading state.
In a cellular wireless packet communication system, a plurality of terminals is present in one cell. At this time, because the radio channel conditions of the respective terminals have different characteristics, it is necessary to perform data transmission of the FDS scheme with respect to a certain terminal and data transmission of the FSS scheme with respect to a different terminal even within one sub-frame. As a result, a detailed FDS transmission scheme and a detailed FSS transmission scheme must be designed such that the two schemes can be efficiently multiplexed within one sub-frame.
In the FSS scheme, a gain can be obtained by selectively using a band favorable to a mobile station (MS) among all available bands. In contrast, in the FDS scheme, an evaluation is not made as to whether a specific band is good or bad, and, as long as a frequency separation capable of adequately obtaining diversity is maintained, there is no need to select and transmit a specific frequency band. Accordingly, it is advantageous to an improvement in entire system performance to perform the frequency selective scheduling of the FSS scheme preferentially when scheduling.
In the FSS scheme, because data is transmitted using sub-carriers consecutively contiguous in the frequency domain, it is preferable that the data is transmitted using CRUs. On the other hand, because data is transmitted using sub-carriers spread the frequency domain, it is preferable that the data is transmitted using DRUs. Therefore, when a FDS transmission scheme and a FFS transmission scheme are multiplexed in a sub-frame, the CRUs and the DRUs are accordingly multiplexed in a frequency division multiplexing manner in the sub-frame.
A distributed resource allocation, such as the FDS transmission scheme, should be applied for a SFH to get a diversity gain the SFH. However, if a SFH is multiplexed with a data channel in a sub-frame in FDM manner and if the resource allocation for the SFH is needed to be pre-defined, it is difficult to apply the same distributed permutation rule as is applied to the data channel to the SFH. This is because the resource location of a SFH is required to be pre-defined. Therefore, to transmit a SFH, it is necessary to define a new resource allocation for a sub-frame including a SFH, which is different from the permutation rule of other sub-frames not including a SFH.